Desarrollo de un fijador eterno Mono-Lateral de fibra de Carbono

This paper reports the design of an innovative mono-lateral external fixator made of carbon fiber composite materials. The designed system can be easily assembled in comparison with commercial fixators and follows orthopedic requirements with sufficient stability and stiffness. The change of operation mode between distraction and fixation is achieved with a wedge that blocks axial translation in one position, while allows sliding with a 90º rotation. The prototypes were produced by the method of molding by compaction. A mold was developed for each part; the rail, the clamp and the cover. Each mold consisted of a cavity that gave form to the piece and a piston that exerted pressure on the composite. Mechanical tests were performed to determine the stiffness under axial compression, and anteroposterior and mediolateral bending. For comparison, tests were also performed on two Orthofix commercial systems, one with the rail made of carbon fiber and the other with an aluminum rail. The axial compression, anteroposterior and mediolateral bending stiffness of the developed system were 200.7, 13.4 and 87.0 N/mm, respectively, which were 38%, 35% and 27% lower than those obtained for the Orthofix system. However, these values were in the range of other similar systems reported in the literature. Therefore, the developed system presented promising results and may be clinically evaluated.Este artículo reporta el diseño de un novedoso fijador externo hecho material compuesto de fibra de carbono. El sistema diseñado es fácil de ensamblar en comparación con sistemas de fijación comerciales y cumple con requerimientos ortopédicos con suficiente estabilidad y rigidez.  El cambio de modo de operación entre distracción y fijación se logra con una cuña que bloquea la traslación axial en una posición, mientras permite deslizamiento si se rota 90°. Los prototipos se construyeron con el método de moldeo por compactación. Se desarrolló un molde para cada parte: el riel, la prensa y la tapa. Cada molde consistió de una cavidad que da la forma a la pieza y un pistón que ejerce presión sobre el compuesto. Se realizaron ensayos mecánicos para determinar la rigidez a compresión axial y flexión anteroposterior y mediolateral. Para comparación, las pruebas se realizaron también sobre en dos sistemas comerciales Orthofix, uno con el riel hecho de fibra de carbono y otro con un riel de aluminio. Las rigideces a compresión axial, flexión anteroposterior y flexión mediolateral  del sistema desarrollado fueron 200.7, 13.4, y 87.0 N/mm, respectivamente, las cuales fueron 38%, 35% y 27% menores que las obtenidas en el sistema Orthofix. Sin embargo, esos valores están en el rango de otros sistemas similares reportados en la literatura. Por lo tanto, el sistema desarrollado presentó resultados prometedores y puede pasar a una etapa de ensayos clínicos

Fabricación y caracterización mecánica de un laminado de fibra de carbono en matriz de resina epoxi

The knowledge about manufacturing and the resulting mechanical properties using fibro-reinforced material is currently limited in Colombia. This preliminary study using beams made of fiber reinforced material was undertaken to evaluate the elastic modulus of the composite material, which will be subsequently used to design an external fixation system for bone transportation. Specimens were made of carbon fiber fabric using epoxy resin as the matrix. A hand lay-up manufacturing process varying number of carbon fiber layers was implemented to evaluate different fiber volumetric ratios. The elastic modulus was experimentally obtained by performing bending tests based on the ASTM D7264 standard. Also, the elastic modulus was theoretically calculated using the rule of mixtures. The experimental and theoretical elastic modulus was lineally increased for increasing the volumetric fiber ratio. However, the experimental results were considerably smaller than the theoretically obtained results, which might be produced by a possible presence of wrinkles or misalignment of the fabric produced during the handling inside the mold. It could be also produced by incomplete adhesion between the fiber and the resin.En Colombia están poco extendidos los conocimientos sobre la manufactura de materiales compuestos fibro-reforzados y sus propiedades mecánicas. Este estudio piloto con vigas de materiales fibro-reforzados se realizó con el fin de evaluar el módulo de elasticidad de un material compuesto con matriz polimérica tipo epoxi y fibras de carbono. Este compuesto   será posteriormente utilizado en el desarrollo de un fijador externo para transporte de huesos. Se describe el procedimiento para la fabricación de los prototipos mediante el procedimiento hand lay-up variando el número de capas de fibra de carbono para variar así la relación volumétrica de la fibra. El módulo de elasticidad se obtuvo experimentalmente mediante pruebas de flexión en tres puntos con base en la norma ASTM D7264 y también se calculó teóricamente utilizando el módulo de elasticidad de los componentes (fibra y resina) y la ley de mezclas.Tanto el módulo de elasticidad obtenido experimentalmente como el obtenido teóricamente, aumentaron linealmente al aumentar la cantidad de fibra en el compuesto. Los módulos de elasticidad experimentales fueron menores que los obtenidos teóricamente, lo cual podría atribuirse arrugas o incorrecto alineamiento de la tela generado durante la manipulación dentro del molde. También podría deberse a una posible incompleta adhesión entre las fibras y la resina

Fabricación y caracterización mecánica de un laminado de fibra de carbono en matriz de resina epoxi

The knowledge about manufacturing and the resulting mechanical properties using fibro-reinforced material is currently limited in Colombia. This preliminary study using beams made of fiber reinforced material was undertaken to evaluate the elastic modulus of the composite material, which will be subsequently used to design an external fixation system for bone transportation. Specimens were made of carbon fiber fabric using epoxy resin as the matrix. A hand lay-up manufacturing process varying number of carbon fiber layers was implemented to evaluate different fiber volumetric ratios. The elastic modulus was experimentally obtained by performing bending tests based on the ASTM D7264 standard. Also, the elastic modulus was theoretically calculated using the rule of mixtures. The experimental and theoretical elastic modulus was lineally increased for increasing the volumetric fiber ratio. However, the experimental results were considerably smaller than the theoretically obtained results, which might be produced by a possible presence of wrinkles or misalignment of the fabric produced during the handling inside the mold. It could be also produced by incomplete adhesion between the fiber and the resin.En Colombia están poco extendidos los conocimientos sobre la manufactura de materiales compuestos fibro-reforzados y sus propiedades mecánicas. Este estudio piloto con vigas de materiales fibro-reforzados se realizó con el fin de evaluar el módulo de elasticidad de un material compuesto con matriz polimérica tipo epoxi y fibras de carbono. Este compuesto   será posteriormente utilizado en el desarrollo de un fijador externo para transporte de huesos. Se describe el procedimiento para la fabricación de los prototipos mediante el procedimiento hand lay-up variando el número de capas de fibra de carbono para variar así la relación volumétrica de la fibra. El módulo de elasticidad se obtuvo experimentalmente mediante pruebas de flexión en tres puntos con base en la norma ASTM D7264 y también se calculó teóricamente utilizando el módulo de elasticidad de los componentes (fibra y resina) y la ley de mezclas.Tanto el módulo de elasticidad obtenido experimentalmente como el obtenido teóricamente, aumentaron linealmente al aumentar la cantidad de fibra en el compuesto. Los módulos de elasticidad experimentales fueron menores que los obtenidos teóricamente, lo cual podría atribuirse arrugas o incorrecto alineamiento de la tela generado durante la manipulación dentro del molde. También podría deberse a una posible incompleta adhesión entre las fibras y la resina

BIOMODE : Biomechanical Modeling of Deglutition.

Deglutition or swallowing is the process in which, coordinate motion of several muscles transport the food bolus, from the oral cavity to the low esophageal sphincter. This process is composed by several stages such as food bolus preparation, propulsion, pharyngeal and esophageal stages. In general, any physiological or pathological affection to this coordinated process is known as dysphagia, and it is associated with stroke survivors, Parkinson, multiple sclerosis, and in general aged related diseases. Dysphagia severely affects the life quality of the patient and can cause death, mainly to the effects of food bolus aspiration (aspiration pneumonia). This research was done in collaboration with GIPSA-LAB, who work under the macro project “eSwallHoome”, funded by the French Agence Nationale de la Recherche (FANR) The research has as the main objective to study and explain the mechanisms of breathing and swallowing via in vivo, in vitro and in simulacra approaches. The project Biomechanical modeling of deglutition (Biomode) is focused on modeling the behavior of food bolus during the swallowing process. This project aimed to contribute to the understanding of the physical phenomena underlying swallowing. Particularly, this project developed tongue’s elastic models and simplified models related with the interaction of a liquid, Newtonian food bolus and the oral cavity during the oral propulsion stage. The approach of the study was both experimental and computational. The highlights of the project included: 1. Mechanical models of tongue’s motion and deformation based on hyperelastic muscle’s properties. 2. Numerical tools for the simulation of large displacement models coupled with nonlinear elastic materials that would potentially describe the fluid structure interaction during oral propulsion stage and also compare the results with experimental data taken from a simplified bench and 3. Generation of simplified dimensionless models of oral propulsion stage based on the interaction between a Newtonian fluid food bolus and the physiological accurate tongue’s dynamics, responsible for oral propulsion. During the project, GIPSA-Lab/TIMC-IMAG laboratories from Grenoble and Nicolas Hermant from Universidad del Valle, developed a full 3D nonlinear elastic model using finite element method and high displacement models of human tongue biomechanics. Also, a basic fluid structure interaction with Newtonian fluid and a nonlinear latex membrane with high displacement model was implemented in ANSYS® Workbench. Finally, two novel simplified dimensionless models for estimation of fluid/tongue interaction load as function of flow regime and fluid food bolus properties were proposed

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Ciencia Odontológica 2.0

Libro que muestra avances de la Investigación Odontológica en MéxicoEs para los integrantes de la Red de Investigación en Estomatología (RIE) una enorme alegría presentar el segundo de una serie de 6 libros sobre casos clínicos, revisiones de la literatura e investigaciones. La RIE está integrada por cuerpos académicos de la UAEH, UAEM, UAC y UdeG

Mis casos clínicos de especialidades odontológicas

Libro que muestra la atención de casos clínicos particulares referente a las diferentes especialidades odontológicasLibro que muestra la atención de casos clínicos particulares referente a las diferentes especialidades odontológicasUniversidad Autónoma de Campeche Universidad Autónoma del Estado de Hidalgo Universidad Autónoma del Estado de Méxic

Failure analysis and redesign of a wagon wheel shaft for sugar cane transport

In this study, a failure analysis of the wheel shafts of wagons for transporting sugar cane is carried out. Several shafts have broken with a small fatigue propagation zone and a large sudden-fracture zone. The material and load condition of the shafts were examined. Stress measurements on a vehicle with a similar suspension system were conducted to fi nd the dynamic loads and calculate the impact factor. An impact factor higher than the one reported in the literature was found. According the manufactures, AISI 1045 steel was the material of the shaft; however, it was found that the material of some shafts did not have the specifi cations of AISI 1045 steel. Moreover, even if the shafts were made with good quality AISI 1045 steel, the stresses are so high that the element will fail due to fatigue. Finally, some recommendations are given to increase the reliability of the shafts, and a new design and manufacturing process are propose

Investigación de la falla de un eje piñón conectado a una extrusora de doble tornillo

Se investigó la causa de falla a un eje piñón de un reductor conectado a una extrusora utilizada en la producción de polipropileno biorientado. El eje se fracturó en el cuñero cerca de la zona de cambio de sección. Se realizaron ensayos de tracción y dureza, análisis metalográfico y microscopia electrónica de barrido (SEM). Además, se efectuó el modelamiento con elementos finitos para determinar el estado de esfuerzos y se realizó el análisis de vida a fatiga del eje. Se encontró que la causa de falla fue por fatiga debido al alto contenido de inclusiones no metálicas de sulfuro de manganeso en el material lo cual ocasionó disminución en la resistencia a la fatiga del eje

Wear and Grip Loss Evaluation of High Chromium Welding Deposits Applied on Sugar Cane Rolls1

Wear on sugar cane rolls is an expensive maintenance problem for the sugar cane industry. Wear produces loss of sucrose extraction and loss of grip of the roll on the bagasse. This paper presents the evaluation of wear and loss of grip of hypoeutectic and hypereutectic high chromium welding deposits applied on ASTM A-36 steel and gray cast iron. A modified ASTM G-65 standard test was used. Wear was produced by the abrasive action of wet bagasse with three levels of mineral extraneous matter. Silica grains with sizes in the range of 0.212-0.300 mm (AFS 50/70) were used as mineral extraneous matter. Grip was evaluated by measuring the torque on the power transmission shaft that moves the specimens. Worn surfaces were characterized by using scanning electron microscopy. Wear was found to increase proportionally related to the mineral extraneous matter content. Geometric changes of the weld deposits related to wear caused grip loss. For low mineral extraneous matter level, wear resistance of carbon steel was greater than that of gray cast iron; whereas the opposite was found for high mineral extraneous matter level.